1. Field of the Invention
The present invention relates to a dielectric recording medium for recording information in a dielectric material, and a method of and an apparatus for producing the dielectric recording medium.
2. Description of the Related Art
Recently, many types of dielectric materials have been developed, and most of them are used for ultrasonic elements, optical elements, a memory and the like. In accordance with the fact, a method of measuring a spontaneous polarization distribution of the dielectric material and local anisotropy of the piezoelectric material has been developed. Also, by using this technique, techniques of recording information in the dielectric material and reproducing the information have been developed.
In order to record information in the dielectric material, a polarization direction of the polarization domain of the dielectric substance is formed such that the polarization direction corresponds to the information. For example, when using as a recording medium a ferroelectric bulk single crystal such as LiTaO3, which has a 180-degree domain, the Z-cut single crystal is mechanically polished to prepare a thin film, and then, its back surface is applied onto a conductor substrate with a conductive paste to hold. The medium as formed above is used as a dielectric recording medium.
Alternatively, after the back surface of a crystal material of the dielectric substance is applied onto the conductor substrate with the conductive paste to hold, a thin crystal is formed by ion beam etching or the like from the side of the front surface. The medium as formed above is also used as the dielectric recording medium.
As described above, in order to record information in high density in a microdomain, it is necessary to form the recording medium as thin as possible, as well as to make the diameter of a probe for recording and/or reproducing small. Therefore, the mechanical polishing, the etching with ion beam and the like are conventionally used to prepare the thin film.
However, the method by the mechanical polishing is limited in thinning the medium with a thickness on the order of several μm, even using an angle polishing method of polishing a crystal with its back surface inclined slightly to the surface of a polishing apparatus. It is also difficult to make it thinner while keeping a stable form because the lack of crystal strength causes fracture.
Moreover, in order to polish the crystal to be in a predetermined thickness, it is necessary to measure the crystal thickness directly in the middle of polishing, as occasion demands. However, it takes a long time to measure it. Especially, in the case of treating a large crystal whose one side is on the order of mm, it is extremely difficult to polish all of the crystal surfaces in a uniform thickness to prepare the thin film.